The present invention is related at least generally to helicopter control systems and, more particularly, to an emergency collective actuator and associated method for a helicopter.
It is recognized in the prior art such as is exemplified by U.S. Pat. No. 4,667,909 (hereinafter the '909 patent) that a sudden power failure during the flight of a helicopter requires the immediate attention of the pilot to convert to autorotation by lowering the collective pitch of the main rotor blades of the helicopter. A failure to timely reduce the collective can result in stalling the rotor blades. Such stalling of the rotor blades will generally produce a catastrophic crash wherein the helicopter, quite literally, falls from the sky. One example of such an accident, which likely involved a rotor stall, occurred in the United Kingdom in March of 1998 and is the subject of AAIB Bulletin No. 11/98. Such an accident will generally be fatal to anyone onboard the aircraft. The particular helicopter that was involved in this accident was the Robinson R22, which is a lightweight helicopter having a low-inertia rotor system. It should be appreciated that a low-inertia rotor system can be stalled more easily than a rotor system having a greater level of inertia. The subject accident report outlines operational conditions for the Robinson R22 under which rotor speed will decay to an unrecoverable value in less than 1 second during a climb.
The prevalent teaching in the prior art with regard to avoiding rotor stall appears to be to simply instruct the pilot to lower the collective setting of the rotor immediately in the event of an engine failure to preserve inertia in the rotor system. In practice, Applicants believe that it is questionable how effective this advice might be relative to low rotor inertia helicopters since engine failure appears to be relatively uncommon. Hence, it is difficult for the pilot to immediately react to a situation that has never been fully experienced firsthand. Even during training, Applicants believe that few student pilots are provided with actual experience either in simulation or actual flight that would realistically duplicate an actual engine failure. The lack of such training is attributed to a certain enhanced level of danger that accompanies the training itself, since full down auto-rotation landings require considerable skill in low rotor inertia helicopters and might result in damage to the helicopter. In this regard, flight instructors are advised to warn a student pilot prior to initiating training exercises relating to power failure simulation, at least in the Robinson R22.
The '909 patent appears to be consistent with the prior art in recommending that the pilot should react immediately and seeks to alleviate the problem by relocating the collective control. Applicants believe that this approach is of limited value since the collective control is traditionally located by the pilot's left hand. It is believed that most experienced pilots would object to relocating this critically important control, since reaction time could at least arguably be increased simply by moving the collective control to a non-traditional location.
The foregoing examples of the related art and limitations related therewith are intended to be illustrative and not exclusive. Other limitations of the related art will become apparent to those of skill in the art upon a reading of the specification and a study of the drawings.